Postharvest regulated deficit irrigation in peach tree in a Mediterranean environment: effect on vegetative growth and yield

The aim of this paper was to verify the possibility to reduce irrigation water requirements by applying regulated deficit irrigation (RDI) during phenological stages less sensitive to water deficit. The effects of two different levels of RDI were studied in a peach orchard (cv Springcrest). From bud break to harvest, irrigation was managed by applying 100% ETc, while from harvest to early autumn, irrigation was equivalent to 100%, 50% and 25% ETc. During the trial, no significant reductions in yield or quality were found for the 50% ETc treatment, whereas about 1,000, 1,800 and 2,400 m3 ha-1 of water were saved in the first, the second and the third year. The 25% treatment did reduce quality and yield significantly. Under scarce water supply conditions, a clear benefit can be obtained through the use of 50% RDI during the post-harvest period, especially for early harvest peache

Variability of total soil respiration in a Mediterranean vineyard

Total soil respiration (TSR) is the major component of the CO2 global flux. The knowledge of the temporal-spatial variability of TSR allows for a better interpretation of a critical component of global greenhouse gas flux measurements. The objective of the research was to evaluate the TSR dynamic over a long measurement period in a vineyard in the South of Italy. A static home-made automatic system was used to measure TSR for a three year period. A portable gas analyser (Li-Cor 6400-09) was used to study TSR spatial variability. A non-invasive geophysical technique (Electromagnetic Induction – EMI) was applied to search for a significant relationship between apparent soil electrical conductivity (ECa), the EMI signal and TSR. Long-term measurements of TSR enabled to study its temporal dynamics. CO2 rates ranged from 0.78 to 43.7 g CO2 m–2 day–1. TSR increased during spring and decreased by 45–50% during the mid-summer. The daily trend of TSR showed differences between the seasons studied reporting a clearly variation among TSR measured on row and inter-row positions. The supplemental irrigation significantly affected (P < 0.001) CO2 soil effluxes which showed a weekly mean increase of 300%. Significant inverse relationships were found by interpolating TSR values and ECa (coefficient of correlation ranging from –0.43 to –0.83 at P < 0.001). The spatialisation of TSR at field scale was performed using the linear regression between TSR values and EMI signals. TSR spatialisation gave a more detailed view of CO2 emissions distribution within the vineyard. EMI technique could be a useful tool to compute accurately the global CO2 emissions which are a complex and hard to measure component of the agrosystem carbon balance

Immobilization of a biomimetic catalyst on clay minerals. Study of the activity of the supported catalysts on the oxidative coupling of humic molecules and precursors.

Two novel heterogeneous biomimetic catalysts were synthesized by immobilizing a meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of manganese (III) chloride [Mn(TDCPPS)Cl] on both kaolinite (K) and montmorillonite (M) clay minerals, previously functionalized with a molecular spacer ending with an imidazole group, whose nitrogen atom firmly coordinated the metal in the porphyrin ring. The clay functionalization by a 3-(1-imidazolyl)propylcarbamoyl-3′-aminopropyl-triethoxysilane spacer was proved by DRIFT-IR, 13C- and 29Si-CPMAS-NMR spectroscopies, and the percent of Mn(TDCPPS)Cl immobilized by the spacer coordination was calculated. The activity of the novel catalysts was evaluated in the oxidative coupling reaction of catechol, a humic phenolic precursor, in the presence of H2O2 as oxygen donor. The rate of catechol oxidation catalyzed by both K and M heterogeneous catalysts was about four times as rapid as that catalyzed by the free manganese-porphyrin in a homogeneous catalysis, and depended on the percent of catalyst immobilized on the clay minerals. Moreover, the activity of the heterogeneous catalysis remained effective for at least two sequential reaction cycles, although a rate decrease in catechol transformation was observed. Afterwards, Mn(TDCPPS)Cl immobilized on spacer –functionalized kaolinite was employed to catalyze the oxidative polymerization of a lignite humic acid under H2O2 or exposure to UV light. The humic polymerization was followed by high-performance size exclusion chromatography (HPSEC), with both spectrophotometric and refractive index (RI) detectors. A significant increase of apparent weight-average molecular weight (Mw) of the humic acid following the oxidative polymerization under heterogeneous biomimetic catalysis, after 72 hours of reaction time. The enhancement in the apparent molecular mass of humic matter subjected to catalyzed oxidative polymerization was also confirmed by HPSEC chromatograms recorded after acetic acid addition to lower the solution pH to 3.5. These results showed that the immobilization of a biomimetic catalyst on clay minerals increased the catalytic efficiency and allowed the catalyst recycling and reuse for additional reactions. Moreover, the heterogeneous biomimetic catalysis increased the molecular mass of a humic acid by formation of intermolecular covalent bonds, thus suggesting its potential use for the soil carbon stabilization and the consequent reduction of CO2 emissions from arable soils

Oxidative and photoxidative polymerization of humic suprastructures by heterogeneous biomimetic catalysis

The meso-tetra(2,6-dichloro-3-sulfonatophenyl)porphyrinate of manganese(III) chloride [Mn-(TDCPPS)Cl] biomimetic catalyst immobilized on spacer-functionalized kaolinite clay mineral was employed in the oxidative coupling reaction of a dissolved humic acid (HA) suprastructure with either chemical (H2O2) or UV-light oxidation. The changes in molecular size of humic matter subjected to catalyzed oxidative reaction were followed by high-performance size exclusion chromatography (HPSEC) with UV-vis and refractive index (RI) detectors in series, and by thermogravimetric (TGA) analysis. Both the enhanced molecular size shown by differences between HPSEC chromatograms of humic reaction mixtures at either pH 6 or 3.5 and the increase of thermogravimetric stability suggest that the heterogeneous biomimetic catalysis promoted the stabilization of humic conformations by new intermolecular covalent bonds during oxidative coupling. The similarity between chemical and light-induced oxidation results suggests potential multiple applications of the kaolinite-supported heterogeneous catalyst in controlling the reactivity of natural organic matter within biogeochemical cycles and environmental reactions

Oxidative and Photoxidative Polymerization of Humic Suprastructures by Heterogeneous Biomimetic Catalysis

The meso-tetra­(2,6-dichloro-3-sulfonatophenyl)­porphyrinate of manganese­(III) chloride [Mn-(TDCPPS)­Cl] biomimetic catalyst immobilized on spacer-functionalized kaolinite clay mineral was employed in the oxidative coupling reaction of a dissolved humic acid (HA) suprastructure with either chemical (H₂O₂) or UV-light oxidation. The changes in molecular size of humic matter subjected to catalyzed oxidative reaction were followed by high-performance size exclusion chromatography (HPSEC) with UV–vis and refractive index (RI) detectors in series, and by thermogravimetric (TGA) analysis. Both the enhanced molecular size shown by differences between HPSEC chromatograms of humic reaction mixtures at either pH 6 or 3.5 and the increase of thermogravimetric stability suggest that the heterogeneous biomimetic catalysis promoted the stabilization of humic conformations by new intermolecular covalent bonds during oxidative coupling. The similarity between chemical and light-induced oxidation results suggests potential multiple applications of the kaolinite-supported heterogeneous catalyst in controlling the reactivity of natural organic matter within biogeochemical cycles and environmental reactions

Vegetative and Reproductive Growth Potential of ‘Montepulciano’ Grapevines Trained to the Tendone Trellis System

A study was conducted to evaluate the vegetative and reproductive capacity of ‘Montepulciano’ grapevines trained to the Tendone trellis system. The study was conducted during 2001 and 2002 in a 6-year old drip-irrigated vineyard located in southern Italy. Vine density was 1,600 vines per ha. Three crop load treatments were imposed at fruit set: UT – unthinned control with approximately 70 clusters per vine (~ two clusters per shoot), T50 – in which 50% of the clusters were removed (~ one cluster per shoot) and T75 – in which 75% of the clusters were removed (~ one cluster every two shoots). Vegetative and reproductive growth was evaluated by measuring leaf area development, leaf gas exchange and water potential, canopy light interception and shoot and cluster growth. Leaf area development was measured by collecting shoots from mature vines on a monthly basis, beginning 15 days after budbreak until the end of September. Transmitted photon flux density (PFDt), on a 0.10 m by 0.20 m grid at the soil surface, and incident PFD (PFDi) above the canopy were measured with a Ceptometer (Decagon D., Accupar) to calculate the intercepted light (PFDin). Gas exchange parameters were measured on both shaded and sun-exposed leaves. Preliminary results indicate that vines trained to the Tendone system have a high capacity to produce vegetation and fruit. Intercepted light reached a maximum value of about 80% at maximum leaf area index (LAI). Thinned vines had significantly greater shoot leaf area, LAI and PFDin as compared to the unthinned control. There were no differences among treatments regarding leaf water potential, photosynthetic rate and apparent quantum efficiency